Biological treatment using bacteria and other microorganisms (biomass) to remove biodegradable organic contaminants through assimilation is known in waste water treatment. The biomass degrades and converts the organics in the waste water into CO2, and also incorporates part of the organics as biomass.
Fischer-Tropsch (FT) synthesis is a process which converts synthesis gas, containing hydrogen and carbon monoxide, into hydrocarbon products. The FT process produces hydrocarbons which may be processed further to produce products such as synthetic crude oil, olefins, solvents, lubricating oil, industrial or medicinal oil, waxy hydrocarbons, oxygen-containing compounds, motor gasoline, diesel fuel and jet fuel. However, a significant product of the FT process is water, hereinafter referred to as “Fischer-Tropsch reaction water” or “FT reaction water”. FT Synthesis has been described extensively in literature, such as “Fischer-Tropsch Technology” by A. P. Steynberg & M. E. Dry, Studies in Surface Science and Catalysis 152, Elsevier (2004).
The products of the FT process are typically subjected to preliminary separation, for example phase separation, wherein the FT reaction water is separated from the rest of the FT products. FT reaction water contains some hydrocarbons including oxygenated hydrocarbons such as aliphatic, aromatic and cyclic alcohols, aldehydes, ketones and acids, and to a lesser extent aliphatic, aromatic and cyclic hydrocarbons such as olefins and paraffins. The composition of FT reaction water is dependent on the catalyst metal used in the FT reactor and the reaction conditions employed. Notwithstanding, all FT reaction water is unique in that it contains substantial amounts of short chain fatty acids (SCFA) or volatile fatty acids (VFA) and alcohols. Since these SCFAs and alcohols typically cannot be recovered economically, FT reaction water is usually treated biologically.
FT reaction water is produced immediately upon the start-up of the FT process, and as mentioned above constitutes a significant portion of the FT product. Therefore the treatment of FT reaction water is also required immediately upon the start-up of the FT process. However, due to the presence of the SCFA's and alcohols, the typical biomass or activated sludge used in conventional biological waste water treatment processes, such as treatment of domestic waste water, is not suitable for treatment of FT reaction water. Also, although conventional activated sludge can be cultivated to produce biomass that is suitable for treatment of the FT reaction water, such cultivation of a suitable biomass can take up to three months.
The Applicant has devised a process for cultivating biomass or activated sludge with a synthetic feed stream to produce a biomass that is suitable for treatment of FT reaction water to a specification that is acceptable for environmental release, irrigation or reuse in process cooling.